Tree Talk
25 Mar 2013
Learn the right way to plant trees.
BY MARY LYNN BRUNY Think you’re planting trees correctly? Compare your method with the experts’ and give leafy life-forms a leg up with these tips from two local arborists.
- When choosing a tree for your lot, consider its mature height in the planting location. Will limbs grow into power lines? Will roots entangle septic systems or underground pipes? Choose wisely for the location, also taking sun and wind exposure into account.
Choose the Right Tree
“Start with the right tree for the right location. Considerations include final size; sun, soil, water and drainage requirements; and wind exposure—a serious issue on the Front Range. It’s easy to get excited about planting a tree not typically found in this region, especially one you had in your distant hometown. But it’s pretty depressing when it dies out here in our semiarid climate. A good resource for proper tree selection is the Colorado State University Extension (www.ext.colostate.edu; type “trees” into the search bar). And don’t forget about aboveground electrical lines that branches may grow into, and underground pipes and septic systems that root systems might entangle. Morin: Look at the tree’s overall height and structure. Is it going to grow into the house or something else? I see this on a daily basis—trees outgrowing their locations Berkelhammer: A good way to choose a tree is to observe ones that are doing well in your neighborhood and have someone identify them for you. But pay attention to their growth habits and exposures.Plant at the Right Time
Spring and fall are the best seasons to plant, when day and nighttime temperatures are cooler. Hot and dry summer days are stressful to new trees, and planting trees in summer reduces their chances of establishing successfully.
Morin: Although both spring and fall are good planting times, spring is a bit more preferable, as we typically have more soil moisture then. That helps out a new tree.
Berkelhammer: Most retail nurseries dig their trees (for sale) in early spring, so the roots are in better condition then. By fall, the roots of trees in pots are circling around the container, dooming them to choking themselves. Or, the trees that are balled-and-burlapped have long roots growing out of the bottom, which isn’t good either.
Choose a Healthy Tree
Choose a tree that has a good single leader or trunk (as opposed to multiple branches), because it will be stronger. You want good, U-shaped unions (also called crotches) between the trunk and branches. Make sure the trunk is free of scars and the leaves are insect- and disease-free. Generally, the smaller the tree the more likely it is to survive transplanting and begin rapid growth. Larger trees take longer to acclimate and begin growing, as they experience more root damage during transplanting.
- These trees stayed in containers too long, as indicated by their spiraling roots that won’t be able to expand outward into the soil, dooming the trees to ill health or death. It’s best to buy container trees in spring, when roots are in prime condition.
Help Root-bound Trees
When you remove a container tree from the pot, you may see spiraling roots at the bottom, which means the tree is root-bound. If planted as is, these roots will not properly grow; instead, they’ll stay in a tangled mess and the tree’s overall growth, strength and health will be forever compromised. Many gardeners are squeamish about disturbing or cutting roots, especially those of something as large and expensive as a tree, but it should be done. Morin: In this case it’s very important to disturb the roots in the top 6 inches of the soil—actually rip them apart. You can cut them with hand clippers and then pull them apart. This helps the roots grow out into the soil. Berkelhammer: Or, you can take a sharp knife and score the entire root ball in thirds. Cut from top to bottom, but not all the way in to the center—just enough to cut those roots that are wrapped on the outside. Then spread the roots out radially when you plant.
- Before buying balled-and-burlapped trees, make sure the roots are solidly anchored. Grasp the trunk and wiggle it; the entire root ball should move solidly with the trunk.
Plant Correctly
Common planting wisdom entails digging a hole twice as deep and wide as the root ball, and planting the tree near or below ground level. Today’s arborists use a more successful method. Instead of digging a “cup” shape, they dig a wide “saucer” shape that is slightly less deep than the root ball. Stick your finger in the tree’s soil until you find its topmost root; this should be even with, or up to 2 to 3 inches above, ground level when planted. After placing your tree in its shallow saucer hole, backfill it with loosened dirt, and incorporate organic matter like compost. Your tree will appear to be on its own small mound. Berkelhammer suggests creating a small, mounded ring around the extreme outside edge of the planting hole to help the tree retain water during the first year. But don’t make the mound too high; you want water to flow outside this ring as well to encourage root growth. Morin prefers making this ring with mulch, because it creates a more porous barrier that water can flow through.” Morin: Roots grow out away from the tree more than they grow down. When planting, dig a hole that’s at least one-and-one-fifth times the diameter of the root ball. Two to three times the diameter is even better. Berkelhammer: If you’re going to err, err toward planting too high. People have this tree-planting ethic and they just dig and dig and dig. Tree roots need oxygen, as well as water. When you dig too deep the roots can’t get oxygen, which is near the surface, so they’ll suffocate and die.Stake Properly
If you’ve ever staked a tree, you probably thought you did a good job when you tightly fastened the tree to a couple of metal T-stakes. Unfortunately, you overdid it. Instead, stake loosely, the experts say. Morin recommends staking two-thirds up the tree trunk; Berkelhammer recommends staking lower, just 12 to 16 inches above ground, and prefers easily removable wooden stakes, as opposed to metal T-stakes, which can rip out tree roots when removed. Morin: Staking is a good idea for the first year the tree is in the soil. But remove stakes after that to avoid strangling the tree. The reasoning behind not leaving stakes on a tree is because trees respond to movement and stress by making “reaction wood”—where they put more growth into the stem to support the tree. Trees staked too long will develop weaker growth. Berkelhammer: Research shows you should stake low and allow the trunk to move in the wind. If you brace your tree too strongly or stake too high, the trunk doesn’t harden as a response to the stresses of nature, and will be weak and prone to breakage. Typically trees only need to be staked one to two years.Mulch the Planting Hole
Spread mulch approximately 3 inches thick in the planting-hole area around your tree. Mulch conserves water, provides a weed barrier and conditions the soil as it composts. Synthetic-fabric weed barriers negate the healthy benefits of mulch and cause more problems than they solve, including fungal growth. Using rocks around trees is not recommended; they increase the heat factor.Tubby Trees
- Trees that are properly staked and planted above grade, with excess dirt mounded and mulched into a ring for water retention, will probably survive. The tree pictured above will probably not survive, because it was planted too deep and the plastic twine that wasn’t removed is girdling the trunk.
